The present invention relates to a fragranced lacquer coating based on an unsaturated polyester acrylate prepolymer in a mixture of polymerizable divinylether monomer, ultraviolet (UV) photoinitiator, and process for preparation thereof.
The process of fragrance coating by offset procedure of microencapsulated fragrances is known, but that method is limited to a layer thickness of maximum 3 xcexcm, and thus the fragrance content is less than 8% (w/w) of the coating composition. This lacquer contains fragrance in relatively low concentration. Another inconvenience of this method is the fact that generally used binding material has odor which sometimes disguises the original fragrance.
Another process of fragrance coating is known, i.e., fragrance dispersion into acryl dispersed phase. The disadvantage of this process is that a high water content (from 50 to 60% by weight) of the mixture enables printing on particularly thick paper of more than 100 g/m2. This flexo-procedure allows limited coating amount comprising of low fragrance content due to the danger of spontaneous coagulation.
The following references disclose compositions comprising a fragrance, but do not describe coating compositions comprising a vinyl ether component in combination with an unsaturated polyester.
JP 01045471 A (J""471) discloses a fragrant resin film prepared by photopolymerizing cyclodextrin and a perfume in a liquid resin comprising a (meth)acrylated oligomer or unsaturated polyester oligomer, a reactive diluent and a photoinitiator. The film is used to give an aroma to cards, posters, etc., by printing onto a substrate.
Safta et al. describe free radical UV radiation curable polish compositions which comprise an unsaturated polyester, monomers or oligomers having (meth)acrylate or vinylether functional groups, a photoinitiator (such as benzophenone) and a fragrance.
FR 1 493 743 discloses resin compositions containing a perfume, an unsaturated polyester and styrene and ethylmethacrylate as reactive diluents.
Photopolymerizable compositions comprising unsaturated polyesters, vinylether monomers and photoinitiators are known in the art.
Murphy et al. (U.S. Pat. No. 4,761,435) describe polyamine-polyene ultraviolet curable coating compositions. Unsaturated polyesters, a vinylether such as diethyleneglycol divinylether and preferably a polytertiary amine resin including ethylenic unsaturation which is polyester are used, polymerization is initiated by an aryl ketone such as benzophenone.
EP 0 322 808 discloses a coating composition comprising unsaturated polyester and vinylether monomers which are cured by EB or by UV in the presence of photoinitiators at a rage of 20 feet per minute in air.
Dougherty et al. (U.S. Pat. No. 4,885,319) describe a blend of divinylether and their use as diluents for irradiation curable resins.
Trade literature xe2x80x9cRAPI-CURE Vinylethersxe2x80x9d describes that: (1) vinylethers combine excellent application properties with low toxicity in comparison to other diluents; (2) vinylethers may be used with most oligomer types, especially epoxides, acrylate and unsaturated polyesters, (3) free radical reactions with acrylate monomers and oligomers.
We found a process based on a liquid, unsaturated polyester in prepolymerization state. Coating in the art and polymerized lacquer allows a slow, retarded elimination of fragrance by membrane diffusion. The real advantage of the named process is unlimited concentration and type of fragrance (synthetic and/or natural).
The object of the present invention is a fragranced lacquer coating polymerized by UV (UV-A, from 315 to 380 nm) radiation comprising
a) 70 to 90 parts by weight unsaturated polyester acrylate,
b) 5 to 22 parts by weight divinylether monomer,
c) 3 to 10 parts by weight UV photoinitiator,
d) 1 to 10 parts by weight fragrance and
e) 0.01 to 0.1 parts by weight odorless additive having fluidifying properties.
The sum of the amounts a+b+c being 100, d+e are premixed and then added in an amount to obtain a properly fragranced lacquer to be coated by UV radiation at temperatures of from 20 to 30xc2x0C.
As polyester base (a) can be utilized unsaturated, for instance amine-modified polyester acrylates, preferably polyester having an aliphatic chain, where the carbon atom number is less than 20.
Unsaturation of polyesters may derive from a) ethylenically unsaturated groups, such as allyl, vinyl and styryl unsaturation, and/or b) polymerizable unsaturated acidic part, such as maleic, fumaric, cinnamic esters. These unsaturated polyesters are useful alone or in combination with other unsaturated reactive components, such as acrylates, preferably containing nonvolatile compounds. The amine-modified unsaturated polyester acrylates are commercially available product, such as Ebecryl 80 (UCB Chemicals, Belgium) including an appropriate amine compound and/or group to minimize oxygen inhibition and thus, tender the coatings rapidly curable on exposure to i UV radiation in the presence of air.
For polymerization and crosslinking as an odorless monomer, divinylether (b), preferably triethylene glycol divinylether and diethylene glycol divinylether, can be utilized.
The good hardness and adhesion of coating is due to crosslinking polymerization. This three-dimensional polymer is able to retard fragrances, as the coatings described in this invention.
As UV photoinitiator, benzophenone derivatives can be used, by-products of which are preferably odorless.
Different fragrances can be used, the invention enables utilizing fragrances of both synthetic and natural origin. Their slight influence on polymerization process must be taken into consideration, therefore, the concentration of each component may vary and trial polymerization is recommended.
An additive is used to improve the aesthetic appearance of the coated material and fluidifying properties of the coat. The fluidifying properties of the coat include the viscosity and surface tension characteristics that allow it to be applied to surfaces as adherent and thin film. Preferably used additives are, for instance, colloidical silica, odorless reactive double unsaturated polyester, fluoroaliphatic polymeric esters.
The process according to the present invention can be carried out by dissolving the vinylether monomer in the liquid unsaturated polyester, then the initiator and the premixed additive and fragrance are added at room temperature (from 20 to 30xc2x0 C.), homogenization with continuous mixing and avoiding UV light. The homogeneous, viscous liquid is coated in a layer from 4 to 20 xcexcm and radiated from 1 to 10 seconds.
In order to avoid overheating due to the infrared component of the UV radiation emitted from mercury vapor UV lamps commonly used for polymerizing, one can utilize UV lamps having a reduced infrared emission or place a filter eliminating most of the infrared radiation to avoid overheating of printed material to more than 40xc2x0 C.